Generally, a tube is connected to a liquid supplying apparatus that functions to supply a liquid medicine (or blood) into a human body. A distal end of the tube is plugged by a cap before injection of the medicine. The tube is then used by removing the cap therefrom and connecting the distal end of the tube to an inlet of a member (e.g., catheter), which has been directly connected to the human body, when the medicine is injected. Before connecting the tube to the catheter, an injection (liquid medicine) is caused to flow downward to exhaust air remaining in the tube. If air is injected into the body of a patient, a dangerous situation may occur in the patient. Generally, during the air-exhausting process, there is some loss in the liquid medicine. In such a conventional cap, it is impossible to perform sterilization with gas in a state where the cap has been installed.
A structure proposed by the present inventor in order to solve the problem is disclosed in Korean Utility Model Registration No. 20-0226977. In the proposed structure, a distal end cap is provided with an air pass filter and an air vent to conveniently exhaust air existing in a tube. That is, as a liquid medicine is supplied to the tube from a liquid supplying apparatus, air existing in the tube is pushed by the supplied liquid medicine and then moves toward the cap. Consequently, the air escapes from the tube through the air pass filter and the air vent. Since only the air escapes therefrom, it is possible to easily exhaust the air without a resulting loss in the liquid medicine. Such a structure has remarkable effects superior to those obtained by conventional caps. However, there are sometimes cases where air remains between portions of liquid medicine within the tube. In such a case where air remains between portions of liquid within the tube, the air pass filter and the air vent may become clogged with a first portion of liquid upon exhaust of the air and thus the air remaining between the portions of liquid may not be exhausted. In this case, there may be inconvenience upon exhaust of the air remaining between the portions of liquid medicine in that the cap is opened and the portion of liquid medicine prior to the air is removed, and subsequently, the cap is closed again and the air is then exhausted. To solve this inconvenience, there is a need for a further improved distal end cap enabling the exhaust of air existing between portions of liquid in a tube without separating the cap from the tube.